AIR PERFORMANCE 123 



Fill in the V column with a few values chosen so as prob- 

 ably to include the speed for best climb. Then fill in the P p and 

 P columns by referring to the propeller and machine performance 

 curves for these values of V. Then work out the columns in 

 succession : for this it may be necessary to use logarithms in 

 order to obtain sufficient accuracy. 



Finally, plot C against V to find the maximum value of C, 

 the rate of climb in feet per minute, and the value of V at which 

 it occurs. For work in standard density air, this value of V is 

 the Air Speed Indicator Reading for best climb. 



The same procedure exactly applies to an altitude, but in 

 this case the propeller and machine performance curves for the 

 altitude must of course be used instead of those for standard 

 density air, while the value of V obtained is the true air speed, 

 not the Air Speed Indicator Reading for best climb. 



Third Approximation. The procedure in this case is really 

 first to obtain a machine performance curve corrected for the 

 full power climbing slip stream and then to apply the First 

 Approximation to the result or the Second Approximation in- 

 stead if the machine is a very strong climber indeed. 



With the usual notation, write down the numerical values of 

 RX, S', k imax , d, and W and then work out and write down the 

 numerical values of 



a _ ijy.SooS'W and ^ _ _T2i. 

 d* d' 2 



Then construct a table in the following form (see next page). 



Next fill up the X column as indicated and the L/D column 

 with corrected values taken from the wing characteristic work. 

 Then turn to the calculation of the machine performance curve 

 done by the First Method or the Second Method (the Third 

 Method or the Fourth Method must not be used, as part of the 

 slip stream is already allowed for in them) and fill in the V and 

 P columns. Now turn to the propeller performance curves and 

 fill in the P p column for the values of V in the V column. Then 

 work out the remaining columns in succession. 



Finally, plot P x on V 1} forming a new machine performance 

 curve which is practically correct for climbing conditions, and 

 then apply to it the method of the First Approximation. 



The procedure at an altitude is to repeat the whole of this 

 work, starting from the machine performance curve calculated on 

 the First Method or Second Method and the propeller perform- 

 ance curves, all for the altitude in question instead of for standard 

 density air. 



